GP1670F_1870F Operator's Manual - Furuno USA

7. FISH FINDER OPERATIONS7.5 Automatic Fish FinderYour fish finder can be adjusted automatically, allowing you to do other tasks.7.5.1 How the automatic fish finder worksThe automatic fish finder function automatically adjusts the gain, clutter, TVG andecho offset. The main features of the automatic mode are as shown below.• Gain adjusts the sensitivity of the receiver to show the bottom echo in reddishbrown,the strongest echo (default color arrangement).• Clutter automatically reduces low-level noise like plankton.• The TVG function is automatically adjusted.• The echo offset balances the gain on high and low frequencies.• Range is adjusted automatically to always show the bottom echo.7.5.2 How to select an automatic fish finder modeThere are two types of automatic fish finder modes: Cruising and Fishing. Cruisingtracks the bottom, and Fishing searches for schools of fish. Cruising uses a higherclutter removal setting than Fishing. Do not use Cruising when your purpose is to findfish, because the clutter removal circuit can erase weak fish echoes.To select an automatic mode, open the RotoKey menu then select [Auto Mode] followedby [Fishing] or [Cruising].7.5.3 How to adjust the gain in the auto modeThe gain controls how echoes of different strengths are displayed. Gain is automaticallyadjusted; however, you can fine tune the gain according to meet local characteristics,etc. Set the gain to show a slight amount of noise on the screen. Increase thegain for greater depths and lower the gain for shallow waters.To adjust the gain, open the RotoKey menu then select [Gain 50k] or [Gain 200k] followedby the soft control labeled with the frequency you want to adjust. The correspondingadjustment windows appears. Rotate the key clockwise to increase the gain,counterclockwise to decrease it.7-8